This invention relates to a process for the isolation of carbon nanotubes from a mixture containing carbon nanotubes and graphite particles.
Carbon nanotubes are recently discovered, hollow graphite tubules having a diameter of generally several to several tens nanometers. One method for the preparation of carbon nanotubes is disclosed by Ebbesen et al (Nature, 358, 220(1992)). In this method, the carbon nanotube crude product having a nanotube content of at most 5% by weight is ground and is sonicated in ethanol to remove graphites particles. However, since part of the graphite particles are held in aggregated carbon nanotubes, it is difficult to separate pure carbon nanotubes in a high yield. The carbon nanotubes obtained by the above process still contain a significant amount of graphite particles. No effective methods have thus far been proposed for the Isolation of carbon nanotubes in a highly pure form.